Field of the Invention
The present invention relates to an electrostatic chuck, and in particular to an aluminum nitride electrostatic chuck used in high temperature and high plasma power density semiconductor manufacturing process.
The Prior Arts
In the early stage of manufacturing semiconductors, the plasma power density utilized is rather low, such that there is no need to perform cooling and temperature control for the wafer. However, in recent years, due to the progress and development of the technology and equipment of manufacturing semiconductors, the plasma power density utilized has increased markedly, so that it is imperative to perform cooling for the wafers, to raise the heat dissipation efficiency for the wafer clamp; otherwise, the temperature increase could damage the pattern structures on the wafer, hereby adversely affecting the subsequent manufacturing process.
Further, along with the increase of the wafer size, the conventional mechanical clamp used to hold wafer has quite a lot of problems, such as, Bowing and Deforming, Edge Exclusion (edge of wafer can not be utilized for being subjected to uneven force), Low Throughput, Complex Structure, Costly Maintenance, Contamination (wafer tends to produce minute particle contamination due to frictions with the mechanical clamp), and Short Life Span.
In order to solve the problems mentioned above, in manufacturing semiconductors, an electrostatic chuck (ESC) having a dielectric layer providing electrostatic force is used to replace the conventional mechanical clamp. In this electrostatic chuck (ESC), the electrostatic force is produced to absorb wafer. As such, in addition to redressing the problems mentioned above, it has the advantages of improving contact with wafer, and raising the heat conduction efficiency to enhance cooling. Further, it is not liable to expose directly to plasma, hereby achieving raised throughput, efficiency, and quality of the wafers produced.
In order to solve the surface heat conduction problem for the wafer, in Japanese Patent No. JP 09-232415, a means is used to provide heat conduction gas to the surface of the electrostatic chuck (ESC). Also, radiation type grooves are provided, and an overlapping structure of groove and electrode is used, to shorten the distance between the bottom of the groove and the electrode, in achieving better heat conduction and fast cooling. However, in case high voltage plasma is applied, that could induce gas electric discharge. In this case, even if dielectric insulation thin film is used for the surface of the electrostatic chuck (ESC), insulation failure may still occur. As such, high power density plasma can be applied to achieve electric insulation and control of high temperature in a manufacturing process, only under the condition that the whole set of ESC is made of electric insulation and heat conductive ceramic, and having a design of cooling gas channel.
Moreover, in Taiwan Patent No. 098127179 is disclosed a ceramic electrostatic chuck (ESC). On its surface is covered with a thin Aluminum Oxide layer as the main dielectric layer; while an insulation positioning chuck made of heat conductive ceramic is used to form a ceramic electrostatic chuck, having gas flow grooves. Yet, the disadvantages of it are that, for a composite layer produced in a high temperature manufacturing process, the composition layers contained therein tend to ablate. In addition, after long period of operation, the dielectric layer of aluminum oxide is liable to be worn out completely during wafer transfer, thus leading to short life span. Besides, heat transfer is hindered in the composite layer interface. As such, the durability of the electrostatic chuck (ESC) used in high temperature and high plasma power density manufacturing process is still an issue to cause concern. Therefore, the new generation wafer manufacturing process requires to use an electrostatic chuck, with its whole set made of dielectric ceramic having good electrical insulation and heat conduction, so that it can be operated in a high temperature and high plasma power density environment.
Therefore, presently, the design and performance of electrostatic chucks is not quite satisfactory, and they leave much room for improvement.